The battery life had been excellent, but as of a few days ago its really tanked.

The following changes were made by me prior to the battery life problem starting, but I'm not sure if any of these changes should cause my problem.

Upgraded to the new Cingular desktop and device software
Noticed that the BB now shows EDGE pretty often whereas it used to only show GPRS
Updated to the latest Google map, the one that is "GPS aware"
Updated to the non-beta, paid version, of JiveTalk
Installed, and the uninstalled Caffeine (it could never resolve my location)

The battery decline is not due to being in poor reception areas, since I'm essentially in the same place where the battery life was excellent

Don't know answer to your question. But when I got concerned about GMM draining battery, I started paying close attention for a week. There was a day I went down to 1/4 on the battery indicator and never used GMM. Other days I might have launched GMM for a few minutes and then closed it, and that seemed to make no difference compared to other days when I didn't use it. Some days I was down a 1/4, others a 1/2 at the end of the day, with no obvious correlation to whether I used GMM or not. (I always did a soft reboot at end of the day during this experiment.) My conclusion was there was either a wider variation in power usage in my case than I realized, or error in battery meter, but nothing I could for sure blame on GMM.